In a general electrophotographic process, an electrophotographic photoreceptor undergoes processes including at least cleaning, charging, light exposure, development, and image transfer. Each process employs a cleaning blade for removing a toner remaining on the surface of a photoreceptor drum, a conductive roller for uniformly imparting electric charge to the photoreceptor, a transfer belt for transferring a toner image, or the like. From the viewpoints of plastic deformation and wear resistance, such a cleaning blade is usually produced from a thermosetting polyurethane resin.
However, when the cleaning blade formed of a polyurethane resin is used, the friction coefficient between a blade member and a photoreceptor drum increases, whereby defoliation of the blade or generation of anomalous sounds may occur. Also, in some cases, the drive torque of the photoreceptor drum must be increased. Furthermore, the edge of the cleaning blade is caught in a photoreceptor drum or the like, resulting in drawing and cutting, whereby the edge of the cleaning blade may be damaged through wearing.
In order to solve the aforementioned problems, efforts have been made for imparting higher hardness and lower friction to a contact part of the polyurethane blade. In one proposed method, a polyurethane-made blade is impregnated with an isocyanate compound, to thereby cause reaction between the polyurethane resin and the isocyanate compound, whereby the hardness of the surface and a portion in the vicinity of the polyurethane resin blade are selectively enhanced. As a result, their friction can be reduced (see, for example, Patent Document 1).
However, when the hardness of the blade surface is enhanced, chipping of the blade occurs easily, which is problematic. Also, when the friction of the blade surface is reduced, occurrence of filming (i.e., a phenomenon of toner adhesion onto a photoreceptor drum) can be prevented. However, undesired release of toner tends to occur, problematically causing cleaning failure.
Another proposed cleaning blade has specifically regulated properties including dynamic hardness and friction coefficient of the polyurethane resin blade surface (see, for example, Patent Documents 2 to 5). However, even though properties including dynamic hardness and friction coefficient of the polyurethane resin blade surface are limited, a satisfactory blade has not been always realized. In actual setting, generation of chipping and filming after long-term use cannot be satisfactorily prevented.
Meanwhile, the performance required for a cleaning blade employed in a conventional printer or the like differs from that required for a cleaning blade employed in a process cartridge. Therefore, the material of the cleaning blade employed in a process cartridge must have high elastic modulus, and is required to have wear resistance, chipping resistance, photoreceptor surface wear resistance, and filming resistance.